The frequent occurrence of large earthquakes (surface wave magnitude, Ms⩾7.0) along the Xiaojiang Fault zone (a key boundary fault system of the Tibetan Plateau) poses a serious threat to social security. However, the absence of long-term continuous records of such events increases the uncertainty surrounding the seismic behavior in this region. Paleoseismic investigations based on trenching are challenging due to subsurface rupturing during large earthquakes, destruction of on-fault deformation features, and the complex distribution of fault branches. Recent paleoseismic studies have suggested that event deposits in Yangzong Lake may preserve evidence of large historical earthquakes within the Xiaojiang Fault zone. Here, we present a 25,000-yr continuous record of large earthquakes in the fault zone, based on radiocarbon-dated event deposits identified by lithology, color, structure, mean grain size, sorting, Mn and Zr contents, and C/N ratio. These data are derived from two sediment cores from the depocenter of Yangzong Lake, supplemented by a reflection seismic image of the lake basin, and improve upon earlier trench-based paleoseismic records. The paleoseismic events recorded in Yangzong Lake (primarily originating from the middle segment of the fault) exhibit a weakly periodic recurrence pattern, with intervals ranging from 333±3 to 6320±651 yr and averaging 1765±460 yr. Integrated paleoseismic sequences from historical, trench-derived, and lacustrine records indicate an increase in seismicity along the Xiaojiang Fault zone during the Holocene, culminating in an unprecedented frequency of large earthquakes over the past millennium. This period of heightened seismic activity coincides with a notable intensification of human presence in the region. These findings highlight the urgent need for a comprehensive reassessment of paleoseismicity and seismic hazard in the area.

Humans evolved rapidly and significantly between 60 and 20 ka, placing unprecedented demands on detailed climate evolution during the marine isotope stage (MIS) 3 period. In this study, a high-resolution loess record from the eastern margin of the Tibetan Plateau revealed that the climate was optimal in 62-43.5 ka, relatively stable in 43.5-34 ka, and continuously cooled in 34-20 ka. Such a three-stage pattern can be well correlated with changes in the temperature and CO2 content in Antarctica, climate evolution in Europe, and advances in the Laurentide Ice Sheet. The climate transition at 43.5 ka was closely related to the declining boreal summer insolation, CO2 content, temperature, and sea level, whereas the climate transition at 34 ka corresponded to a decrease in the CO2 concentration and development of polar ice sheets. These results are of great scientific significance because they provide insights into MIS 3 climate transitions and human migration.

Holocene weak Indian summer monsoon (ISM) precipitation has been linked to increased El Niño occurrence on centennial timescales. However, historical data document episodes of extreme precipitation in ISM-dominated southwestern China during El Niño summers. To resolve this discrepancy and better understand the spatiotemporal patterns of El Niño–Southern Oscillation (ENSO)-related climate extremes, we present a 12,000-yr high-resolution reconstruction of floods and monsoon precipitation from Yangzong Lake in southwestern China, based on grain-size and elemental proxies. By comparing this record with other paleoclimatic archives across the Asian monsoon region, we identify a trend of increasing floods superimposed on a long-term decline in Holocene monsoon precipitation. This pattern coincides with a hydroclimatic seesaw: floods in the ISM-dominated southwest and droughts in the East-Asian-summer-monsoon-dominated northeast, correlating with an increase in El Niño events. Previous studies using modern observations and numerical simulations indicate that under El Niño conditions, the strengthened and southwestward-shifted West Pacific subtropical high blocks northeastward moisture transport from the Bay of Bengal, concentrating rainfall over southwestern China, while simultaneously impeding northward moisture flow from the western tropical Pacific, leading to droughts in northeastern China. This mechanism is supported by the shared harmonic quasi-periodicities between these extreme climate events and ENSO activity.

Understanding the ecological effects of strong earthquakes and post-seismic vegetation dynamics in mountainous areas is essential for mitigating post-earthquake disasters. Here, a detailed palynological and radiocarbon-dating study was carried out on the tufa sediments from Huohuahai Lake, Jiuzhaigou National Nature Reserve, China. Rapid transitions in palynological assemblages, from high contents of shrubs and herbs to Quercus, Betula and Pinus tree pollen, have repeatedly occurred over the past similar to 1650 years. These short-term variations, combined with historical seismic records, probably record post-seismic (open forest) and inter-seismic (mixed forest) periods. Strong earthquakes caused damage to forests and induced hydrological changes, resulting in low pollen concentrations and increases in shrubs and herbs after such events. Subsequently, mixed coniferous broad-leaved forest gradually developed during inter-seismic periods. A particularly large earthquake occurred in similar to 520 CE near Jiuzhaigou, and the vegetation recovery time from this was up to similar to 214 years; this recovery time could also have been influenced by the sudden cooling and gradual drying climate and/or a previous strong earthquake. Our findings confirm the high seismic risk in the Min Shan uplift zone and the important driving force of tectonic activity on forest succession in mountainous areas.

Five M s 7.0 earthquakes (Wenchuan, Yushu, Lushan, Jiuzhaigou and Maudo) have occurred on the eastern Tibetan Plateau since 2008, and > 20 historical earthquakes (M s >= 5.0) have also been recorded, demonstrating the strong seismic activity prevalent in this region. Owing to the geomorphology of the region, consisting of alpine valleys with a lack of Quaternary deposits, it is difficult to conduct paleo-earthquake research through the excavation of trenches. Lacustrine sediments are regarded as the most suitable archives for paleo-earthquake studies because they often comprise a detailed, long-term, and continuous environmental record. To assess the seismic activity of the Diexi, we studied a well-exposed outcrop of Xinmocun lacustrine sediments that included three sections (XMCI (11.5 m), XMCII (5.6 m), and XMCIII (11 m)) near Diexi Lake, moving from a lake shore to lake center environment, at the intersection between the Minjiang fault and Songpinggou fault. Taking into account the geodynamic setting of the area and its known tectonic activity, soft-sediment deformation structures, including load and flame structures, injection structures, ball structures, pseudo-nodules, boudinage structures, plunged sediment mixture, liquefied breccia and micro-faults, discovered within the sections are interpreted as seismites. High-resolution grain-size and magnetic susceptibility indicators were used to obtain a continuous record of the changes in physical properties within the three sections enabling the recognition of additional seismic events that did not result in soft-sediment deformation structures. Rapidly deposited layers with underlying soft-sediment deformation structures in the sections record five (XMCI, XMCII and XMCIII) seismic events; these comprise siliciclastic-enriched sandy sediment fluxes from earthquake-triggered landslides or dust of siliciclastic-enriched clastic materials. Isolated rapidly deposited layers (without underlying soft-sediment deformation structures) record 18 (XMCII), 12 (XMCI), and 21 (XMCIII) additional earthquake-induced inputs of detrital material into the lake. Optically stimulated luminescence and 14 C dating of the XMCI, XMCII, and XMCIII sections indicate continuous sediment deposition from 19.4-9.9 ka, 15.5-10.1 ka, and 18.7-10.6 ka, respectively, and the seismic events recorded in these sections can be cross-correlated within the age error range. Hence, there are a total of 30 seismic events recorded within the Xinmocun sediments during the period 18.6-10 ka, suggests a weakly periodic pattern with an apparent recurrence time of similar to 280 years. The Minjiang fault and Songpinggou fault are Holocene active faults with a risk of causing strong earthquakes. Due to the Diexi area is located at the intersection of the Minjiang fault and Songpinggou fault, and has frequent seismic activity, suggest a high seismic risk in the future.

The Qinghai Lake is located near the junction of the East Asian summer monsoon (EASM), East Asian winter monsoon (EAWM), and Westerlies. The aeolian deposits around Qinghai Lake hold significant value in tracking the paleowind direction, which is crucial to reconstruct paleo-atmospheric circulations. In this paper, a systematic study of anisotropy of magnetic susceptibility (AMS), rock and environmental magnetism, grain size distribution, and X-ray diffraction was conducted on a loess sequence (named Heimahe) in the Qinghai Lake area. The AMS results of the Heimahe section reveal two prevailing winds of NE-SW and NW-SE orientations during the last deglacial in the Qinghai Lake area. Grain size distribution and mineral composition analyses suggest that the NE-SW and NW-SE winds are respectively associated with the winter monsoon and the Westerlies. Moreover, the variations in magnetic lineation as well as other AMS parameters indicate that the dominant paleowind direction in the Qinghai Lake region during the last deglacial changed periodically with a similar to 300 yr frequency. It appears that magnetic fabric is capable of recording rapid changes in paleowind direction.

Lakes, being key regulators of atmospheric carbon dioxide (CO2), have not yet been intensively explored in the carbon cycle. This study provides an attempt to investigate how carbon sequestration in mountain lakes responds to seismic activities, extreme climate events and human disturbance. The new data of grain-size end members (EMs), TN contents, C/N, concentrations of algal spores, and P and Mn contents, in addition to previously published data of TOC and Ca contents, Zr/Rb, Rb/Sr, and land-pollen assemblages of a well-dated sediment core from Yileimu Lake, depicted a more detailed history of environmental evolution in the region. A great earthquake happened in southern Altay at similar to 3500 cal yr BP that triggered extensive landslides around the lake, and then frequent floods eroded the catchment between similar to 3500 and 2300 cal yr BP, subsequently severe drought events occurred within the period of 2300-1000 cal yr BP, finally agricultural and pastoral activities intensified within the last 1000 yrs. Organic carbon accumulation rate (OCAR) in Yileimu Lake was extremely high (an underestimated value of similar to 370 g m(-2) yr(-1)) during the earthquake event, in response to the rapid accumulation of landslide materials. Regional comparison revealed that summer temperature was unexpected to have determined the OCAR during both flood and drought events (average 4.07 and 3.64 g m(-2) yr(-1), respectively), because it dominated the production of land- and aquatic plants. Human activities increased the OCAR prominently (averages 6.26 g m(-2) yr(-1)) via changing sediment production and vegetation planting, which decoupled the OCAR from climate factors. These data imply that carbon sequestration in lakes from mountain areas where temperature adversity stress dominated vegetation growth would have the potential to increase under anthropogenic warming. In addition, seismically induced carbon sequestration in lakes from tectonically active regions cannot be ignored.

To explore the main controlling mechanism of hydroclimatic conditions during the last deglaciation on eastern Tibetan Plateau (TP), clay mineral records in Xinmocun lacustrine sediments were analyzed. The results indicate that high illite + chlorite contents (>92%) in the section represent the primary product of strong physical weathering in a tectonically active area. The chemical weathering index (IC) was used to monitor hydrological changes in the section. Under the transition from glacial to interglacial periods, the fluctuation amplitude of IC during humid periods was greater than that during dry periods. The IC demonstrates changes in hydrological conditions on a millennial scale. From 18.7 to 16.8 ka, high values of IC and illite crystallinity suggest strong hydrolysis in humid conditions. From 16.8 to 11.7 ka, low IC values suggest weak hydrolysis during a fivemillennium long dry period, which was followed by a more humid period from 11.7 to 10.5 ka. The overall arid hydrological conditions during the last deglaciation on eastern TP probably resulted from northward shift of the intertropical convergence zone driven by enhanced insolation, leading to the extension of the Indian monsoon to the interior of East Asia. Our findings suggest that the Indian summer monsoon has dominated hydrological conditions on eastern TP since the onset of deglaciation at approximately 16.8 ka.

It is strongly debated whether the Westerlies and the East Asian summer monsoon (EASM) are in-phase, anti-phase or out-of-phase, and how hydroclimatic changes in the above two climate systems affected trans-Eurasian cultural exchanges during the late Holocene. In this study, we establish a 3500-a-long paleoclimatic sequence based on high-resolution analyses of sedimentological and geochemical data of a well-dated sediment core from Yileimu Lake in southern Altay. High percentages of the >63-mu m fraction and high values of Zr/Rb and Rb/Sr ratios indicate strong transport of weakly weathered, coarse sediments into the depocenter of the lake caused by enhanced surface runoff and catchment erosion associated with a wet climate, and vice versa. High values of Ca and total inorganic carbon (TIC) contents imply increased precipitation of endogenic carbonates in the lake water under intense evaporation associated with a dry climate, and vice versa. This new record indicates two wet intervals at 3500-2300 and 600-100 cal a BP, interrupted by a severe and prolonged dry interval from 2300 to 1000 cal a BP, and a mild dry interval with occasionally wet conditions from 1000 to 600 cal a BP. These results are broadly consistent with other paleoclimatic records in Westerlies-dominated Asia and are generally anti-phase with those in the EASM region. We suggest that a strengthening/weakening and southward/northward migration of the Westerlies during a negative/ positive phase of the North Atlantic Oscillation (NAO) transported more/less water vapor into arid Asia. Meanwhile, a decreasing/increasing El Nino-Southern Oscillation (ENSO) superimposed on a southward/northward shift of the Intertropical Convergence Zone (ITCZ) triggered a weakening/strengthening and southward/northward movement of the West-Pacific subtropical high (WPSH), resulting in decreasing/increasing EASM intensity. In addition, the wet climate from 3500 to 2300 cal a BP may have contributed to the development of nomadic herding in the eastern Eurasian Steppe and Altay region, and to the opening of the proto-Silk Roads. Potentially, intense seismic activities in the Altay Mountains similar to 3500 cal a BP may have also promoted the opening of the proto-Silk Roads by forcing the herdsmen to move to the inter-mountainous basins. The strong EASM intensity from 2300 to 1000 cal a BP in eastern China may have contributed to the creation of the ancient Silk Roads by the Han Dynasty. (C) 2022 John Wiley & Sons, Ltd.

The onset of a modern-type paleoclimate in Asia has been traced back to the Late Oligocene-Early Miocene, and is characterized by a monsoonal climate in eastern Asia, and an arid to semiarid climate in mid-latitude Asia. However, the climatic characteristics at the transitional boundaries of these two regions remain poorly constrained. In this study, we compiled a series of pollen assemblages from four sites spanning a width of 900 km in the northeastern Tibetan Plateau to analyze precipitation patterns during the Mid-Miocene (18-14 Ma). The pollen assemblages were dominated by desert-steppe (DS) taxa in the basin, while coniferous and broadleaved trees dominated in the mountains, with DS taxa decreasing eastwards. According to quantitative relationships between the DS taxa percentages of 2059 surface pollen samples and precipitation, the mean annual precipitation was estimated to be 305 mm in the westernmost portion of the study area, 380-440 mm in the central portion, and 632 mm in the easternmost portion. This indicates a clear precipitation gradient, with absolute values that strongly contrast with those of the present day (50, 90-180, and 480 mm, respectively). We argue that moderntype paleoclimate gradients in arid mid-latitude Asia might have formed as early as the Mid-Miocene, with precipitation being five times greater than at present in the westernmost part of the region. Our Mid-Miocene reconstruction shows a stronger monsoonal climate system than that of the present day, while the boundary between the monsoonal and arid/semi-arid regions was over 10 degrees west of its present-day position.

Climate and landscape changes since the late Holocene have received increasing attention. The Altai region, which is located at the intersection of the Inner Asian Mountain Corridor and the Eurasian Steppe Roads, is relatively poorly studied. In this study, based on robust radiocarbon ages and detailed pollen analyses, the history of climate and landscape changes was reconstructed from Yileimu Lake, southern Altai Mountains during the past 3500 years. Four stages of vegetation change are identified: (1) During 1550 BCE-720 BCE, the vegetation was taiga (mainly Picea and Betula) in uplands, and steppe (dominated by Artemisia, Poaceae and Cyperaceae) around the lake, indicating a humid climate, which was favorable for the expansion of human activities including enhanced nomadic pastoralism in Altai Mountains and transcontinental culture exchange along the proto-Silk Roads. (2) During 720 BCE-390 CE, there was a stepwise decrease in Picea, rapid increase and then decrease in Betula, and gradual increases in contents of Poaceae and Thalictrum pollen, and fern spores, indicating a warm and moderately humid climate, with evidence of more intense human activities during 20 BCE-390 CE. (3) During 390 CE-1560 CE, desert-steppe (with high Amaranthaceae, Caryophyllaceae, Ephedra and Cyperaceae content) developed in response to an increasing arid climate and/or enhanced human activities. (4) After 1560 CE, taiga and steppe recovered due to the humid climate. Human activities have become the key factor affecting vegetation since the past 2000 years. In addition, the vegetation response to an Ms >= 8.0 earthquake that occurred around 1550 BCE was characterized by a rapid recovery of Betula, followed by Artemisia and Picea. Restoration of vegetation helps to reduce soil erosion and afforest exposed landslides.

Lake sediments that widely distributed in the active and complicated fault zones have been recently showing great potential for paleoseismic reconstruction. However, flood events and human activities may make the seismic signal unrecognizable. In this study, high-resolution analyses of sedimentary structure, physical and chemical proxies, as well as absolutely radioactive dating were conducted on seven representative sediment cores from the depocenter, nearshore and inlet areas of Yangzong Lake, a typical fault lake in the Xiaojiang Fault zone, southeastern Tibetan Plateau (TP). These new data were calibrated by historical documents, suggesting that seismically induced mass-transport deposits (MTDs, i.e., turbidites) were massive and/or amalgamated (earthquake doublet), became fining and thickening towards the lake center (without changing lake morphology), and occasionally exhibited soft sediment deformation structures (SSDs, i.e., microfaults). These sediments were relatively poorly sorted and instantaneously deposited from slope failures within the lake. An extremely strong earthquake could cause coseismic subsidence of the lake basin and destruct the local hydrological system, resulting in exceptionally high Mn and total inorganic carbon (TIC) contents in the lake center. In contrast, flood deposits were thinner with horizontal beddings, had higher terrestrial organic matter (higher C/N ratios), and distributed locally in the lake inlet area. Human activities-induced sediments were inversely graded, poorly sorted and gradually deposited, had horizontal beddings and no erosive base, and exhibited high carbon, Pb and Zn contents and low C/N ratios. In addition, macroseismic investigations and statistical results from intensity prediction equations (IPEs) provided a conservative threshold of ∼8 Modified Mercalli Intensities (MMI) for triggering turbidites, and a ∼ 10 MMI for inducing coseismic subsidence and hydrological destruction. This study was among the first attempts to establish a quantitative lacustrine paleoseismograph in the southeastern TP, and the new results would greatly improve the valid assessment of geohazard risks.

To explore the factors controlling the spatiotemporal variability of dust magnetic susceptibility (SUS) across tectonically stable (Chinese Loess Plateau, CLP) and tectonically active (eastern Tibetan Plateau, ETP) regions, the SUS and grain-size records of the Jingyuan and Lantian loess-paleosol deposits from the CLP, and Lixian lacustrine sediments from the ETP, were analyzed. The results show that, spatially, SUS decreases substantially from SE to NW in the CLP, and from the CLP to the ETP; and temporally, SUS increases significantly both in the CLP and the ETP during warm periods. The former is consistent with pedogenic contributions previously proposed, while the later responds to the enhanced seismic activities and foehn effect during warm period. The correlation analysis shows that the strongest positive correlation between SUS and 2-10 & mu;m fractions in the CLP indicates a substantial contribution of fine particles to magnetic minerals, which has been underestimated in the earlier studies. The strongest positive correlation between SUS and coarse-grained fractions in ETP reveals that SUS is mainly controlled by frequent release of magnetic minerals from bedrock caused by tectonic activities. These results reflect different controlling factors of SUS changes under different tectonic backgrounds. Therefore, the correlation analysis between SUS and grain-size fractions can be used as a simple and effective method to sensitively reveal regional tectonic activity, and effectively trace the Earth surface processes including material supply, transport dynamics, and sedimentology.

The Fuyun Fault is a typical intraplate, slow-slipping fault, but has been repeatedly ruptured by surface wave magnitude (Ms) ≥ 8.0 earthquakes. The 11 August 1931 Ms 8.0 Fuyun earthquake resulted in more than 10,000 casualties in the sparsely populated Fuyun area. Cosmogenic 10Be dating of offset landforms produced by prehistoric Ms ≥ 8.0 earthquakes yields an average recurrence interval of 9,700 ± 3,300 years, much longer than previously estimated 2,000–4,500 years, clouding our understanding of the timing and recurrence behavior of past earthquakes originating from the Fuyun Fault. Reflection seismic data reveal widely distributed subaquatic faults in Yileimu Lake, implying high sensitivity of the lake sediments to paleoearthquakes originating from the Fuyun Fault. Two new long sediment cores (Y20A: 267 cm; Y20B: 890 cm) together with previously published two short cores (Y19: 71 cm; Y20: 31.5 cm) from the depocenter and nearshore zone of Yileimu Lake are used for stratigraphic correlations and analyses of sedimentary structures, grain-size distributions, magnetic susceptibility, elemental composition and carbon content. The mass-wasting deposits with underlying soft-sediment deformation structures (SSDS) in the Y20B core indicate six siliciclastic-enriched sandy sediment fluxes from earthquake-triggered landslides of granitic rocks, and isolated SSDS record three additional earthquake-induced in situ deformations. Turbidite-like deposits with sorting indices >3 and Si contents >700 counts per second (cps) are comparable to those of the seismic mass-wasting deposits, and are thus interpreted as seismites from earthquake-induced re-deposition of nearshore sediments. There are a total of 20 seismic events recorded by the Y20B core. Seismic intensity calculation results, combined with historical seismic data, provide potential magnitudes of Ms ≥ 8.0, Ms ≥ 7.0, and Ms ≥ 5.5 for the earthquake-triggered mass-wasting deposits, SSDS, and turbidite-like seismites, respectively, in Yileimu Lake, generally consistent with previously published magnitude thresholds. Radiocarbon dating and stratigraphic correlations constrain the timing of these past earthquakes to ∼28 cal kyr BP. This unique, long lacustrine paleoseismic record suggests a weakly periodic pattern with recurrence intervals between 2,317 and 7,830 years and an average of 5,303 years for potential Ms ≥ 8.0 earthquakes, and reveals an unprecedented high frequency of potential Ms ≥ 7.0 earthquakes originating from the Fuyun Fault in the last 5 kyr, demonstrating the urgent need for an improved assessment of seismic hazards and risks in the Fuyun Fault zone.

General history of disasters in China suggests that China has frequently experienced two major natural disasters in its long history, one is from catastrophic earthquake events, and the other is from extreme climatic events, due to its unique active tectonic environment and climatic complexity. Although these two major natural disasters have caused great damage to human society, it remains unclear whether and how they affect Chinese dynasty alternation on decadal (emperor) timescales. Based on detailed comparisons between abrupt climatic changes, catastrophic seismic activities, and the history of Chinese dynasty alternation from 1000–2000 AD, we conclude that on decadal timescales, extreme drought (and/or flood) events could indeed significantly reduce agricultural production, cause severe food shortages and famine, and result in increases in population exile, rising food prices and inflation, and insufficient supplies for military defense, which could exceed social resilience and eventually lead to financial risks and social upheavals of the dynasties. In addition, catastrophic seismic events in the densely populated, agricultural areas of China, including the 1303 surface wave magnitude (Ms) 8.0 Hongtong earthquake, the 1556 Ms 8.25 Huaxian earthquake and the 1920 Ms 8.5 Haiyuan earthquake, caused more than 200,000 casualties and millions of victims to live in exile which was almost equivalent to the order of magnitude of those extreme climatic events-induced refugees. The secondary geological hazards related to the earthquakes (e.g., extensive landslides and soil erosion), which could last for decades, caused more casualties and reduced food production. Furthermore, great plague spread caused by the casualties could significantly increase psychological panic among the survivors, resulting in social instability. Therefore, catastrophic seismic events could also accelerate the collapse of the dynasties (e.g., the Ming dynasty) without immediate mitigation measures. This study indicates that catastrophic seismic activities, as well as extreme climatic events, could have great effects on the social structures and thus on the Chinese dynasty alternation on decadal timescales, which highlights the far-reaching implications of geological hazard research.

The deposition of fluvial sediments in tectonically active areas is mainly controlled by tectonics, climate, and associated Earth surface processes; consequently, fluvial sediments can provide a valuable record of changes in regional climate and tectonic activity. In this study, we conducted a detailed analysis of the grain-size distribution in modern fluvial sediments from the upper Min River, eastern Tibet. These data, combined with information on regional climate, vegetation, hydrology, geomorphology, lithology, and fault slip rate, indicate that modern regional tectonic activity along upper Min River can be divided into three segments. Specifically, fluvial sediments in the Minjiangyuan–Diexi segment are dominated by silts (< 63 µm, 70.2 %), agreeing with low runoff, low rainfall, and high vegetation cover and revealing a windblown origin influenced by the arid and windy climate. These observations are consistent with the low hillslope angle and low relief, all indicating weak activity along the Minjiang Fault. The coarse-grained fraction (> 250 µm) of fluvial sediments in the Diexi–Wenchuan and Wenchuan–Dujiangyan segments increases stepwise downstream, although runoff and rainfall do not change significantly. These patterns correlate well with increases in both regional relief and hillslope angles. Together, these observations imply that regional tectonic activity along the Maoxian–Wenchuan Fault becomes more pervasive downstream along the Min River. The occurrence of well-sorted and well-rounded pebbles of fluvial sediments downstream of Dujiangyan must be related to the long-time scouring and sorting by rivers. This study marks the first development of a new research approach that can characterize regional tectonic activity by analysis of grain-size distribution of fluvial sediments collected from tectonically active regions.

Palaeogene environmental evolution in East Asia remains ambiguous. Here we present integrative work including magnetostratigraphy, grain‐size, geochemistry, and clay mineralalogy from a 1609 m‐thick fluviolacustrine sequence in eastern China. The results reveal two periods of tectonic control alternating with three periods of climatic control on the sedimentary evolution. Tectonic activity in the study area, as revealed by particle coarsening and reduced weathering, occurred during 65.6–59 Ma and strengthened in Asia during 55–54 Ma in response to the India‐Eurasia collision. Weathering gradually enhanced in East Asia during 59–55 Ma, probably caused by global warming. Continuous global warming during 54–50.5 Ma is responsible for enhanced aridification in East Asia. From 50.5 to 37.6 Ma, global cooling weakened evapotranspiration and increased westerlies‐derived moisture. Both aspects increased effective moisture and chemical weathering in East Asia. These results shed light on how alternating tectonism and climate change impacted environmental evolution in Asia during the Palaeogene.

Quantifying the magnitude of an earthquake is very important for long-term and medium-term earthquake prediction, post-earthquake emergency rescue and seismic hazard assessment. Paleo-seismology is the investigation of past earthquakes in the geological record, in particular their location, timing and size. Uncertainties remain in the paleo-earthquake magnitudes determined by traditional surface rupture parameters, especially because most seismic events do not result in surface ruptures or are of less than 0.3 m (M =  ~ 6–6.8). To address the problem of magnitude evaluation of earthquakes that did not reveal major dislocations, this paper deals with the methods used to determine the seismic shaking intensity based on the types and forms of soft-sediment deformation structures, including maximum liquefaction distance, thickness of disturbed layer, empirical formulae, and thickness of rapidly deposited sand layer. Then we discuss and analyze these methods in terms of their theoretical basis, advantages and disadvantages, accuracy, applicability and problems. We chose two case studies: first, a typical seismics-related deposit (liquefied layer and disrupted layer) represented by a seismite in the late-Pleistocene Lake Lisan section near Masada in the Dead Sea Basin; and second, the liquefied diapir triggered by an earthquake in the late-Quaternary lacustrine sediments at Luobozhai in the upper reaches of the Minjiang River, East Tibet. The five methods listed above are employed to determine earthquake magnitudes associated with the seismics-related deposit and liquefied diapir, yielding magnitudes of 5.5–6.5 and 6.0–7.0, respectively. The combination of the five methods, provided a new and relatively convenient method for determining seismic shaking, especially in lacustrine sediments. This study can serve as a valid reference for comparing methods of calculating the magnitude of a paleo-earthquake based on surface rupture parameters, and provides a better understanding of the long-term seismic activity and risk in tectonically active regions.

It is hotly debated whether the Westerlies and the East Asian summer monsoon (EASM) are in-phase, anti-phase or out-of-phase. In this study, we established a 3500-yr-long paleoclimatic sequence based on ~ 8-yr resolution sedimentological and geochemical data of a precisely dated sediment core from Yileimu Lake in southern Altay. This new record indicated two wet intervals from 3500–2300 and 600–100 cal yr BP, interrupted by a severe and prolonged dry interval from 2300–1000 cal yr BP and a mild dry interval from 1000–600 cal yr BP. These results are broadly consistent with other paleoclimatic records in Westerlies-dominated Asia and are generally anti-phase with those in the EASM region. We suggest that a strengthening/weakening and southward/northward migration of the Westerlies during a negative/positive phase of North Atlantic Oscillation (NAO) transported more/less water vapor into arid Asia. Meanwhile, a decreasing/increasing El Niño-Southern Oscillation (ENSO) superimposed on a southward/northward shift of the Intertropical Convergence Zone (ITCZ) triggered a weakening/strengthening and southward/northward movement of the West-Pacific subtropical high (WPSH), resulting in the decreasing/increasing EASM intensity. In addition, the wet climate from 3500–2300 cal yr BP may have contributed to the development of nomadic herding in the eastern Eurasian Steppe and Altay region, and to the opening of the proto-Silk Roads. Potentially great seismic activities in the Altay Mountainous before 3500 cal yr BP may have also promoted the opening of the proto-Silk Roads by forcing the herdsmen to move to the inter-mountainous basins. The data in this study imply an increasing drought risk in arid Asia with current global warming, which may force local herdsmen to move to the monsoonal areas along the Silk Roads, and trigger cascading socio-economic responses.